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i' Carol Russell and Ed Bischoff -2- April 26, 1982 The Lower reach of the diversion follows the course of an unnamed tributary of Magpie Creek to join ldagpie Creek downstream from both rdning operations. This part of the ~iversion is designed, the original tributary channel was not modified to accommodate additional flow. Bank erosion and channel degradation are likely to occur. As can be readily seen, the Flagpie Creek diversion is somewhat makeshift. This is partially the fault of the Division because, as a part of Dorchester's coal mine interim permit approval, the Division approved a diversion rahich simply ended at the permit boundary. At that time, the diversion was approved as a temporary diversion. However, in its application for a permanent program permit, Dorchester indicates that it intends the diversion to be permanent. Rule 4.05.4(3) provides that permanent stream channel diversions may be constructed with the approval of the Division if such diversions are consistent with applicable State law, would not diminish downstream water rights and meet the requirements of Rule 4.05.4. In determining whether to approve the diversion as a temporary diversion or a permanent diversion, there are several questions that should be considered. 1) Flhat are the probable hydrologic consequences of a permanent diversion? The most likely hydrologic effect would be erosion i77 the lower reach of stream resulting from increased streamflow. This effect could be avoided by enlarging the natural channel. 2) Is the diversion capable of transporting the sediment load supplied from the watershed above? This is most applicable to the upper reach in which the natural gradients have been redrrced. As a practical matter, siltation must be avoided if channel capacity is to be maintained. In addition, Rule 4.05.4(b) would require that the diversion be capable of transporting natural sediment loads. 3) Is the location of the permanent diversion appropriate? The diversion is cut into the ~ase of a steep hillslope and the stability of the hi11s1ope may be affected. Landslides mould reduce channel capacity. 4) Is the diversion properly designed? Neither operator has furnished a complete diversion plan certified by a qualified registered professional engineer. The G.E.C. Dlinerals' application contains four alternative designs for the diversion and numerous other design suggestions; but it does not identify rahich were selected for the design. (The key to making this diversion work is the steep transition section at the Lbrchester - G.E.C. boundary.) In order for the Division to determine whether the Magpie Creek diversion should be approved as a permanent diversion, additional information addressing these issues should be submitted. In either case (permanent or temporary), a certified plan must be submitted by the operators. In this case, "as built" drawings showing whatever modifications are necessary to meet the current performance standards would be appropriate. I am preparing memos for each operator identifying the information that should be included in their application. Let me knora if you have any further questions. /mt cc: Dave Shelton Jim Pendleton